1. Field of the Invention
The present invention relates to a method and an image forming apparatus, such as a copying machine, a facsimile, a printer, and other similar devices, and more particularly to a method and an image forming apparatus that can produce a toner pattern for adjusting a density of toner and/or prevent a cleaning blade from being caught up while preventing an adhesion of the toner to a separation pick.
2. Discussion of the Background
In an electrophotographic image forming apparatus, an electrostatic latent image is formed on a surface of a photoconductive element. The electrostatic latent image is developed into a visible image with toner. The visible toner image is then transferred onto a transfer sheet to form an image on the transfer sheet. In the above-described image forming apparatus, residual toner remaining on the surface of the photoconductive element after the toner image has been transferred is removed by a cleaning device.
Conventionally, in the cleaning device the residual toner is scraped by press-contacting a rubber tip edge of a cleaning blade with the surface of the photoconductive element. However, a friction coefficient between the surface of the photoconductive element and the cleaning blade increases when a film layer of minute toner is formed by heat and pressure on the surface of the photoconductive element. Thus, it may happen that the cleaning blade is caught-up by the photoconductive element. To prevent the above-described phenomenon, a toner pattern (i.e., a cleaning blade caught-up inhibiting pattern) is generally produced on the surface of the photoconductive element to reduce the friction coefficient by adhering toner of the toner pattern to the tip edge of the cleaning blade.
In addition, in a background image forming apparatus, a toner pattern is produced on the surface of the photoconductive element. A density of the toner pattern is detected by a sensor. Then, the density of the toner is adjusted based on the detected value to prevent degradation of an image quality due to background fouling toner and a scattering of the toner inside the apparatus.
In a method for adjusting the density of toner, a latent image is formed in a non-image region of the surface of the photoconductive element. The latent image is then visualized with toner. Thus, the toner is forcibly consumed to achieve a desired toner density. Hence, a toner pattern produced for toner density detection and adjustment is also used as the toner pattern for preventing a cleaning blade from being caught-up.
In Japanese Patent Laid-Open Publication No. 10-228164, a technology for using a toner pattern produced for a detection and adjustment of a toner density also for preventing a cleaning blade from being caught-up is disclosed. In Japanese Patent Laid-Open Publication No. 11-024383, a technology for stabilizing a density of toner by performing a forcible toner consuming operation is disclosed. To be more specific, the cleaning blade caught-up inhibiting pattern is produced in a form of a continued latent image in a main scanning direction of a photoconductive element having a length equal to that of a cleaning blade. As described above, a main objective of producing the cleaning blade caught-up inhibiting pattern is to reduce a friction coefficient between the surface of the photoconductive element and the cleaning blade by using toner of the pattern as a lubricant. Thus, an excessive amount of toner is not used for the production of the cleaning blade caught-up inhibiting pattern.
When consuming toner by producing the cleaning blade caught-up inhibiting pattern, the amount of toner to be consumed is adjusted by adjusting a length of the cleaning blade caught-up inhibiting pattern in a sub-scanning direction. Thus, when a size of the cleaning blade caught-up inhibiting pattern is increased in the sub-scanning direction, the amount of the consumed toner is increased.
However, the production of the cleaning blade caught-up inhibiting pattern results in an adhesion of toner to a separation pick that separates a transfer sheet from a photoconductive element. As a result, the separation pick may not properly function.